The present invention relates to a plasma processing apparatus or a plasma processing method of detecting an etching end point at the time that a substrate-like sample is etched in fabrication of a semiconductor integrated circuit and more particularly to a plasma processing apparatus and a plasma processing method of performing etching processing of a layer structure containing a layer to be processed previously provided on an upper surface of the substrate-like sample such as a semiconductor wafer disposed in a processing chamber within a vacuum container by means of plasma formed in the processing chamber while detecting the processing state.
In the process of fabricating a semiconductor device from a substrate-like sample such as a semiconductor wafer, the dry-etching technique using plasma formed in a processing chamber within a vacuum container is widely used to remove a film layer of various materials, particularly the film layer of dielectric material, formed on the surface of the wafer or form a pattern in the layer. In an etching processing apparatus using such plasma, generally, an electric field or magnetic field is made to operate on processing gas introduced in the processing chamber which is a processing space within the vacuum container to form plasma, so that charged particles such as ions in the obtained plasma or high-active particles (radicals) are reacted with the layer structure containing the film layer to be processed previously disposed on the surface of the wafer to thereby make etching of the layer to be processed.
In such etching processing of the wafer, it is known that the strength of the specific wavelength in emitted light of the formed plasma is changed with the etching progress of the layer to be processed. Thus, there is hitherto known the technique that the change in the light emission intensity of the specific wavelength from the plasma in such processing is detected during the processing and the end point of etching in case where the layer is removed by the etching or a desired depth is reached is detected on the basis of the detection result.
Particularly, in order to achieve higher integration degree and minuteness of processing of a semiconductor device, it is important that processing is ended when remaining thickness of the layer to be processed reaches a predetermined value in the etching processing. As such a technique of ending the etching processing when the thickness of the layer to be processed reaches the predetermined value, there is known the technique that the thickness of the remaining layer is detected using change in the intensity of interfered light (interference light) by utilizing the fact that light from the surface of a wafer containing the layer to be processed forms the interfered waveform in accordance with reduction in the remaining thickness of the layer to be processed with the progress of etching.
Further, there is the process that a silicon substrate is etched and a groove for electrically separating a device on the wafer is formed in the silicon, for example, after application of mask material on the wafer. In this case, it is important that when the silicon substrate is etched by a decided depth amount, the processing is ended.
For example, JP-A-2001-085388 discloses that wavelengths of at least two kinds of interference light are detected and the remaining thickness of the layer to be processed is detected using values of the intensity of the interference light of the plural wavelengths. Further, JP-A-2002-081917 discloses the technique that the interference light of plural wavelengths is detected and patterns of data concerning the intensity of the interference light having previously obtained interference light of plural wavelengths as parameter are compared with data concerning the intensity of actually obtained interference light to thereby detect the remaining thickness of the layer to be processed.
Moreover, JP-A-2010-034582 discloses the method in which known light is received from the outside and three wavelengths of light reflected by a wafer are observed to analyze a frequency so that the depth of etching is calculated. JP-A-2003-83720 discloses the method in which interference light of plasma light reflected by member to be processed is observed and interference wavelengths are separated into a mask component and a step component for wavelength bands to calculate the depth of etching.